The present invention relates to devices attached to and activated by a telephone line and, more particularly, to remote listening devices.
There are many uses for a remotely activated listening device that can be attached to a normal telephone line to be activated by a signal on the line from a standard telephone instrument at a different location and transmit the sounds heard back over the telephone line. Consider the following possible examples of uses for such a device:
Case No. 1--George's mother lives alone, is along in years, and refuses to have anyone check on her during the night. George buys a listening device and connects it to his mother's telephone line. It is set to answer on the fifth ring. His mother is only steps away from the telephone and can answer by the third or fourth ring under normal circumstances. If George wants to check and see if his mother is okay, he need only call her. If she does not answer, the listening device answers and he can hear everything and determine if she is okay.
Case No. 2--Sam owns a small business that has a burglar alarm system. When activated, the alarm calls a central station. Several times in the middle of the night, the alarm has been activated, but the premises were not actually entered. Sam knows that the police frown on false alarms. Accordingly, each time he made a needless trip to find out what, if anything, had happened prior to notifying the police. With a listening device, when the alarm company notifies him of alarm, he merely calls the listening device and listens for signs of a break-in or illegal activity before notifying the police.
Case No. 3--Jim is responsible for checking a water pumping station. His job is to be sure that all pumps are running and the tanks are properly filled. The various pieces of equipment each have small tone alarms or bells that sound in case of malfunction. In this case, an immediate response is not necessary. Jim can simply call about once every four hours to a listening device at the pumping station. He avoids having to drive to the pumping station every few hours as he did in the past. Jim can call from anywhere. The only cost is a monthly phone bill, which is small compared to an elaborate alarm system.
Case No. 4--Acme Corporation is a large manufacturing plant which is unoccupied between 7:00 p.m. and 7:00 a.m., weekdays. Using the company PBX, every 30 to 60 minutes the security guard can call several listening devices that have been placed in specific locations. He listens for unusual activities or sounds.
Case No. 5--Harry and Marge own a mountain cabin. When they are not there, they plug a listening device into their phone line. They can periodically call from their home to see if any unusual noises are present about the cabin.
Case No. 6--Mom and Dad go out for the night and leave junior and sis at home. A listening device is set to answer on the first ring. Mom and dad can call back several times to be sure the home is fairly quiet and all is well. As soon as the phone rings, the kids have been told to say a few words in the direction of the listening device.
Wherefore, it is the object of the present invention to provide a simple, reliable listening device which resists unauthorized use and has features which will accomplish the task of the above-described examples.